Acoustic instruments are instruments that produce sound waves through acoustic means. Some examples of acoustic instruments include drums, pianos, and guitars. Some acoustic instruments may be stringed instruments. For example, acoustic guitars, ukuleles, sitars, banjos, and mandolins are all different types of stringed acoustic instruments. Various stringed instruments may have strings of different lengths and sizes, which may determine the frequency or musical note produced by the vibration of a specific string. The tonal sound of an acoustic instrument may be determined by a number of factors, including the size of the instrument, the material of which the instrument is made (e.g., wood vs. carbon fiber), the shape of the cavity in the body of the instrument, and choice of strings (e.g., metal vs. nylon).
Acoustic-electric instruments are acoustic instruments that are modified with electrical components. Some acoustic-electric instruments may have built-in electronic components, while other acoustic-electric instruments may be modified with modular or removable electronic components. Some acoustic-electric guitars may be fitted with a magnetic pickup, a piezoelectric pickup, or a microphone, for example. Various acoustic-electric instruments may require a power source on board the instrument (e.g., a battery), while other acoustic-electric instruments may rely on an external power supply. An electric-acoustic instrument may include a connector configured to send a signal to an amplifier that may amplify the sound of the instrument. Acoustic-electric instruments may be used instead of purely electric instruments (e.g., an electric guitar) because of the unique characteristic sound of the acoustic-electric instrument. As with purely acoustic instruments, the tonal sound of an acoustic-electric instrument may be determined by a number of factors (e.g., the material of the instrument, etc.). For example, the Ovation® Roundback developed by Charles Hancock Kaman was built from fiberglass (based on his research as an aerospace engineer), and included electrical pickups to provide for the option of amplification.